Many types of fuel pumps are utilized for internal combustion engines to supply fuel to the engine from a remotely positioned fuel tank. As the operating conditions of the engine change, the fuel demand or rate of consumption of the engine changes. Some current fuel systems known as return fuel systems have a return line through which excess fuel supplied to the engine is returned to the fuel tank. Pressure regulators can be used in the return line to control the pressure of fuel supplied to the engine by varying the rate at which excess fuel is returned to the fuel tank. Other fuel systems, commonly referred to as returuless or "No-return" fuel systems, vary the flow rate at which fuel is delivered to the engine in accordance with the engine fuel demand. Pressure regulators can also be used in no-return fuel systems downstream of the pump outlet and upstream of the engine to accumulate excess fuel and deliver fuel at a flow rate corresponding to the engine's demand. Still other systems use a modulated drive system for the fuel pump to vary the power supply to the fuel pump and hence, the speed at which the fuel pump operates and thus the rate of fuel output of the fuel pump. The modulated drive is typically in communication with a computer processor or electronic engine control unit which monitors the operational conditions of the vehicle and communicates that information with the modulated drive to control the pump output as a function of the operating fuel demand under varying conditions of the engine.
In return fuel systems, the fuel returned to the fuel tank is at an elevated temperature especially if the fuel was returned to the fuel tank from adjacent the engine or the fuel rail. The returned fuel generates vapor within the fuel tank which is undesirable for the operation of the fuel pump and which is volatile and environmentally hazardous. Further, simply returning excess fuel to the fuel tank or accumulating excess fuel in a no-return fuel system is an inefficient use of the fuel pump because the fuel pump usually operates under a higher load than necessary and is delivering fuel which is not needed for the immediate use of the engine. This leads to unnecessary power consumption by the fuel pump. This unnecessary power consumption also results in undesirable heating of the fuel. Additionally, modulated drive systems add cost and complexity to the fuel delivery system.